field splitting behavior

field splitting behavior

[Paul Lew - remove nospam when reply]

Take a look at the following:

> var='foo:bar' 
> echo ${(@)${(s/:/)var}[1]}
foo

> var='foobar'
> echo ${(@)${(s/:/)var}[1]}
f

So why it did field splitting on each character when there is no
separator ':' found?  I would expect 'foobar' on the output.

Thanks in advance..

Re: field splitting behavior

[Zefram]

Paul Lew wrote:
>> var='foobar'
>> echo ${(@)${(s/:/)var}[1]}
>f
>
>So why it did field splitting on each character when there is no
>separator ':' found?  I would expect 'foobar' on the output.

The result of the splitting is a single word "foobar", as you expect.
This is then treated as a scalar, not an array, and so the [1] extracts
the first character, instead of the first element.  The (@) doesn't do
what you think it does (it only has an effect where double quotes are
used).  I don't see any easy way to force the result of a ${(s...)...}
to be treated as an array, so I'll have to leave that to the expansion
wizards.

-zefram

Re: field splitting behavior

[Peter Stephenson]

Zefram wrote:
> Paul Lew wrote:
> >> var='foobar'
> >> echo ${(@)${(s/:/)var}[1]}
> >f
> >
> >So why it did field splitting on each character when there is no
> >separator ':' found?  I would expect 'foobar' on the output.
> 
> The result of the splitting is a single word "foobar", as you expect.
> This is then treated as a scalar, not an array, and so the [1] extracts
> the first character, instead of the first element.  The (@) doesn't do
> what you think it does (it only has an effect where double quotes are
> used).  I don't see any easy way to force the result of a ${(s...)...}
> to be treated as an array, so I'll have to leave that to the expansion
> wizards.

I can only think of the gross hack

  print ${${(s/:/):-${var}:rubbish}[1]}

which extends the string to make sure it produces an array.  It's somewhat
inconsistent that you sometimes get a scalar and sometimes an array.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 392070


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